Ethylene glycol (EG) is one of important industrial base materials, which can be used to manufacture products like polyester fiber, antifreeze, unsaturated polyester resin, nonionic surfactant, ethanolamine, explosive, and so on. Traditional EG production employs ethylene oxide (EO) direct hydration process (FIG. 1), but this process has many disadvantages of high water ratio (molar ratio of H2O to EO is up to 22:1), high energy consumption, poor selectivity of ethylene glycol (<89%), and so on.

Recently, various new EG production technologies are successively developed, in which the representative ones are the catalytic hydration process (WO9931033A1) and ethylene carbonate process. Comparing with the direct hydration process, the water ratio in the catalytic hydration process is 3-10, and the selectivity of EG is less than 96%. The disadvantages of the hydration process are the low activity and the stability of the catalysts. The process for producing ethylene glycol via ethylene carbonate (Reaction Formula 2) is a process in which EO and CO2 as raw materials are firstly subjected to a carbonylation reaction for synthesizing ethylene carbonate (EC) and followed by hydrolyzing EC to produce EG. Comparing this process with the direct hydration and the catalytic hydration processes, it has the advantages such as moderate reaction conditions, low water ratio (H2O:EO=1.5:1 to 1.1:1), high EG selectivity (>99%), and low energy consumption. Famous international companies such as DOW, Texaco, Halcon-SD, Nippon Shokubai and Japan-Mitsubishi have already carried on the corresponding investigations. This process represents the development direction of ethylene glycol production.

Because of the flammability, the explosibility, and the toxicity of EO, high efficient conversion of EO to produce EC have become the essential reaction of the EC process. At present the catalysts for producing EC, which have already been reported include homogeneous and heterogeneous types. Among them, the examples of the homogeneous catalysts are halides of alkaline earth metals (U.S. Pat. No. 2,667,497, CN1926125A), transition metal complexes or quadridentate Schiff's alkali metal complexes (CN1416952, CN1415416), organic base (such as DMF and DBAP) (J. Org. Chem. 2003, 68, 1559), organic tin, germanium or tellurium compounds (JP57-183784), ionic liquids such as quaternary ammonium salts (such as tetrabutylammonium bromide, tetrabutylammonium chloride or tetrabutylammonium iodide) (U.S. Pat. No. 2,773,070), imidazolium salts (such as 1-butyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium bromide) (CN200310121060.0), quaternary phosphonium salts (such as tetrabutyl phosphonium iodide, triphenylmethyl phosphonium iodide and triphenylbenzyl phosphonium chloride) (CN1308046A, CN1161320A, JP58-126884, JP2000143563A). As for the heterogeneous catalysts, examples include solid alkalis (such as MgO—Al2O3) (J. Am. Chem. Soc. 2001, 123, 11498, CN101265253), molecular sieve (J. Phys. Chem. B 2005, 109, 2315-2320), anion exchange resin containing quaternary ammonium salts as exchanging groups (JP3-120270), and heteropolyacids based on tungsten oxides or molybdenum oxides and the salts thereof (JP7-206847), and so on.
Catalysts for EC hydrolysis which have been reported include homogeneous imidazolium acidic salts (such as [bmim]HSO4 and [bmim]H2PO4) (CN1978415A), and supported basic imidazolium salts (such as PS-[bmim]OH and PS-[bmim]HCO3) (CN101456792, J. Mol. Cats. A: Chem. 2008, 279(2): 230-234).
For these catalytic systems, more or less, there are problems such as poor catalyst activity, poor stability, severe reaction conditions, strong toxic organic solvent to be used and high catalyst cost. Development of the two step catalysts, which are cheap, high efficient, simple composition and environmental friendship, is urgently desired. On the other hand, in the current EC process, the carbonylation catalyst and the hydrolysis catalyst are generally used separately, because of the catalysts for these two steps are hard to be compatible. Such traditional technology directly results in complex catalyst separation, which leads to the corresponding complex separation process, high energy consumption, as well as influences the quality of EG product.